The present disclosure relates to a sheet conveyance device, a document conveyance device, and an image forming apparatus.
An image forming apparatus having an image reading portion which reads a document (sheet) may be provided with a sheet conveyance device for conveying a document to a reading position of the image reading portion.
A sheet conveyance device of this type has a document conveyance path leading from a document table through a reading position to a sheet discharge tray. On the document conveyance path, a sheet feed roller, a registration roller, and, a plurality of conveying rollers are provided in this order from upstream (document table side) in the conveyance direction. When a document conveyance operation is started, the sheet feed roller feeds a document placed on the document table to the document conveyance path to convey the document in the conveyance direction. The registration roller stops advance of the document in the conveyance direction once, and then conveys the document in the conveyance direction. The reading position is provided downstream of the registration roller. The document having passed through the reading position is conveyed to the sheet discharge tray by the plurality of conveying rollers.
In this configuration, a plurality of documents may be fed in an overlapping manner to the document conveyance path. Therefore, a separating roller for separating one by one the plurality of documents fed in an overlapping manner is provided on a side of the document conveyance path opposite to the sheet feed roller (the sheet feed roller is disposed on the upper side of the document conveyance path and the separating roller is disposed on the lower side of the document conveyance path). Upon the document conveyance operation, the sheet feed roller is rotated in the conveyance direction while the separating roller is rotated in a direction opposite to the conveyance direction. Thus, even if a plurality of documents are fed in an overlapping manner, a document on the upper side to be fed at the present is conveyed in the conveyance direction by the sheet feed roller while a document on the lower side not to be fed at the present is returned in the direction opposite to the conveyance direction by the separating roller.
For example, the separating roller is connected to a torque limiter, so that when a feeding force exceeds a set critical value of the torque limiter, the separating roller is forward rotated (rotated so as to follow a document conveyed in the conveyance direction by the sheet feed roller). However, when a plurality of documents are fed in an overlapping manner so that a document on the lower side not to be fed at the present exists between the separating roller and a document on the upper side to be fed at the present, the feeding force does not exceed the set critical value of the torque limiter. Therefore, the document on the lower side not to be fed at the present is returned in the direction opposite to the conveyance direction by the separating roller rotating reversely.